Preface

This book is the official documentation of PostgreSQL. It is being written by the
PostgreSQL developers and other
volunteers in parallel to the development of the PostgreSQL software. It describes all the
functionality that the current version of PostgreSQL officially supports.

To make the large amount of information about PostgreSQL manageable, this book has been
organized in several parts. Each part is targeted at a different
class of users, or at users in different stages of their
PostgreSQL experience:

PostgreSQL is an
object-relational database management system (ORDBMS) based on POSTGRES, Version
4.2, developed at the University of California at
Berkeley Computer Science Department. POSTGRES pioneered many
concepts that only became available in some commercial database
systems much later.

PostgreSQL is an
open-source descendant of this original Berkeley code. It
supports a large part of the SQL:2003 standard and offers many
modern features:

complex queries

foreign keys

triggers

views

transactional integrity

multiversion concurrency control

Also, PostgreSQL can be
extended by the user in many ways, for example by adding
new

data types

functions

operators

aggregate functions

index methods

procedural languages

And because of the liberal license, PostgreSQL can be used, modified, and
distributed by everyone free of charge for any purpose, be it
private, commercial, or academic.